One of the attempts to capsule the historical development of using electrostatic fields to resolve liquid emulsions is found in Prestridge U.S. Pat. No. 3,847,775 dated Nov. 12, 1974, incorporated by reference, and hereinafter referred to as the dual polarity disclosure. The dual polarity disclosure was drafted at a time when its assignee was exclusively concerned with the reduction of oil-water emulsions. Nevertheless, the terminology and concepts recognized that the oil-water emulsions were included in the broader definition of the emulsions of polar and non-polar liquids.
With the passage of time, the metallurgical recovery systems utilizing solvent extraction techniques were brought to the attention of the assignee of the dual polarity disclosure. In penetration of this market, the assignee has become concerned with the problem of mixing and separating aqueous phases from the solvent phases which is one of the aspects of these metallurgical recovery systems. Again, the solvent-aqueous emulsion also falls under the classification of an emulsion of polar and non-polar liquids. Therefore, the breaking of both the oil-water emulsions and the solvent-aqueous emulsions presents a common problem. Characteristically, and in common with oil field emulsions, these metallurgical emulsions are low in dielectric strength in proportion to the ratio of the aqueous phase to the solvent phase.
Prestridge U.S. Pat. No. 4,126,537 dated Nov. 21, 1978, is incorporated by reference as a technological footprint of the assignee and is part of the art of forming a degraded electrostatic field between electrodes energized by a source of DC. This disclosure attempts an explanation of the problem of coalescing extremely small drops of an aqueous liquid in an emulsion with a non-polar liquid. Essentially, the disclosure explains how the hydraulic shearing forces of the non-polar liquids are prevented from limiting the progressive coalescence of the aqueous phase.
It became evident in the researching for reduction of the metallurgical emulsions that the reduction of the oil field emulsions could also be effected. A long-standing problem in reducing oil field emulsions has been their variable dielectric strength. At a certain lowered value of dielectric strength of the emulsion, the electrostatic field between the electrodes collapses. A substantial amount of literature has discussed the nature of the conductive path formed between energized electrodes in emulsions having a relatively high proportion of aqueous phase. It is difficult to precisely measure when the increasing quantity of the aqueous phase in the emulsion lowers the dielectric strength of the emulsion to the value where a particular level of energy to the electrodes will fail to sustain an electrostatic field. There has been contemplation of the aqueous phase increasing to the value where it apparently becomes the continuous phase of the emulsion and thereby establishes the undesirable low level of dielectric strength. Some workers refer to this as approaching a 1 to 1 ratio. It is not deemed vital to pinpoint the level of dielectric strength which will preclude the maintenance of the electrostatic field between the electrodes. It has simply been discovered that there is a need for an additional electrical insulator between energized electrodes when creating an electrostatic field through which an emulsion of low dielectric strength is passed.
The dual polarity disclosure contemplated the relatively broad classification of emulsions on each side of the 1% cut of aqueous. The disclosure specifically defines the wet emulsion as being that with more than 1% cut while the dry emulsions are those with less than 1% cut. As emulsions were encountered with a cut of substantially more than 1% aqueous, the problem was consigned to the broad limbo where other means and methods were employed to get the cut down close enough to 1% for treatment by the electrostatic field of the dual polarity disclosure.
Also, the dual polarity disclosure left the vague impression that the dry emulsions in the DC electrostatic field could be treated down to a satisfactory level of aqueous content. The demands of both the oil field and mineral industries are now specifying aqueous contents down to 100 ppm or less. At this point, the degraded field disclosure moves to center stage.
The degraded field disclosure somewhat narrowly focuses upon means and methods for systematically reducing the gradient of an electrostatic field as the emulsion passes through the field. The extremely small aqueous dispersions can be moved by the high intensity of the DC electrostatic field if provisions for degrading that field are made to avoid the hydraulic force which tends to shear the aqueous dispersion as it is coalesced to a predetermined size.
The art is now prepared for a significant leap forward by arranging a series of electrostatic fields, some of which were given birth as evidenced by both the dual polarity disclosure and the degraded field disclosure. This advance in the art can be applied even-handedly to both the emulsion of the oil field and the emulsion of the minerals industry, which are broadly classified as emulsions of polar and non-polar liquids.